Calcium sodium alumino disilicate foam

ABSTRACT

A zeolite sodium aluminodisilicate, such as prepared by refluxing meta kaolin in 10% NaOH solution, is at least 50 percent ion exchanged to the calcium form, which is heated at 900*-1150* C. for several minutes to provide a non-zeolitic crystalline low density calcium sodium aluminodisilicate foam. Insulation panels can be made from such unique calcium sodium aluminodisilicate foam.

AU 116 Ex Air Products and Chemicals, Inc., Philadelphia, Pa.

The portion of the term of this patent subsequent to Apr. 13, 1988, has been disclaimed.

Filed: Jan. 25, 1971 Appl. No.: 109,638.

Related 1.1.8. Application Data Continuation of Ser. No. 693,733, Dec. 27, 1967, Pat. No. 3,574,647.

Assignee:

Notice:

US. Cl 106/40, 106/75, 252/62, 252/378 Int. Cl C04b 33/00 Field of Search 106/40, 71, 72, 75, 106/65,:59 DV;23/l11, 112 R, 1132 References Cited UNITED STATES PATENTS 11/1961 Sensel 23/112 R 3,475,225 1011969 Tennenhouse 106/65 3,574,647 4/1971 Flank et al 106/40 2,992,068 7/1961 Haden et a1. 23/112 3,597,155 8/1971 Flanigen 23/111 3,449,070 6/1969 McDaniel et a1. 23/11 1 3,518,051 6/1970 Maher et a1. 23/111 3,594,331 7/1971 Elliott 252/455 3,322,690 5/1967 Bilisoly 252/455 FOREIGN PATENTS OR APPLICATIONS 855,301 11/1960 Great Britain 252/458 R OTHER PUBLICATIONS Evans, R. C.; Crystal Chemistry; Cambridge, 1964, p. 258, (OD 9051583).

Levin, E. M. et al.; Phase Diagrams For Ceramists: Columbes, 1969, pp. 172-174 (QD 501L4).

Primary Examiner-Helen M. McCarthy Attorney-B. Max Klevit and John R. Ewbank [57] ABSTRACT A zeolite sodium aluminodisilicate, such as prepared by refluxing meta kaolin in 10% NaOH solution, is at 1 Claim, No Drawings CALCIUM SODIUM ALUMINO DISILICATE FOAM CROSS REFERENCE TO PARENT APPLICATION This application is in part a continuation of Ser. No. 693,733 filed Dec. 27, 1967 maturing as U.S. Pat. No. 3,574,647 on Apr. 13, 1971, all the disclosure of which is deemed here reiterated. By terminal disclaimer, this case expires simultaneously with said parent.

BACKGROUND OF THE INVENTION 1. Field of Invention This invention relates to pore-forming methods for modifying aluminodisilicate ceramics, and to the ceramic foam composition resulting therefrom.

2. Prior Art Foam glass and many other varieties of inorganic foam are predominantly amorphous. Thermal recrystallization simultaneously with formation of ceramic foam is quite distinguishable from the better known routes toward expanded vermiculite, low density perlite, and related materials. Prior workers have recognized that the sodium aluminodisilicate described as an intermediate for the manufacture of ultrarnarine in Kumins et al.,lndustrial and Engineering Chemistry 45, 567-572 (1953) and Kumins et al. U.S. Pat. No. 2,544,695 has some resemblence to the Zeolite A of Milton U.S. Pat. No. 2,882,243. Some of the disclosures linking the Kumins type of sodium aluminodisilicate with Zeolite A include Howell U.S. Pat. No. 3,114,603, Howell et al. US. Pat. No. 3,119,660, and l-laden et al. U.S. Pat. No. 2,992,068.

SUMMARY OF THE INVENTION A non-zeolitic crystalline calcium sodium aluminodisilicate having low density, low surface area, minimized moisture sorption propensities, and open pore structure is prepared by heating at 900-l150C. for l-l20 minutes a zeolite corresponding to (CaO (Na O) A1 0 2SiO yl-l O in which y has a value such that the water content is about 0.2-3 percent by'weight of the zeolite.

DESCRIPTION OF PREFERRED EMBODIMENTS The nature of the invention is clarified by reference to Examples l-Vlll of said parent application, previously deemed reiterated. Examples lX-Xlll of the parent application concern interesting compositions outside some of the chemical limitations herein. The invention is further clarified by reference to the following examples.

EXAMPLES XIV-XV Following the procedure of Example 1 of Kumins U.S. Pat. No. 2,544,695, kaolin is calcined to 800C. for 3 hours to prepare a catalytic grade of meta kaolin, which is dispersed in an aqueous solution containing percent sodium hydroxide, and the mixture is agitated and maintained at about reflux temperature for about 16 hours. The solid sodium zeolitic product is filtered from the solution and corresponds generally to the Zeolite A material of U.S. Pat. Nos. 3,1 14,603 and 3,119,660. The sodium zeolite is treated with a series of solutions of CaCl, and then with water to prepare a calcium sodium zeolite in which at least 50 percent of the ion exchange capacity is occupied by calcium and in which at least 10 percent of the ion exchange capacity is occupied by sodium. The product is water washed to provide a calcium sodium zeolite corresponding to the formula (Ca0),. (Na,0),. M "O,,, A1 0,. 2SiO yl-l O in which r is at least 0.5 and s is at least 0.1 and l-r-s is 0, and in which n is the valence of the miscellaneous metal. The value of s is always greater than lrs. The values of r and s respectively are 0.7 and 0.3 after four steps of one hour of ion exchange with a 100 percent stoichiometric excess of hot solution of 1 molar CaCl Any of several miscellaneous metal ions can be introduced by ion exchange and if their total molar concentration is less than the sodium concentration, the suitability of the material for the present invention is not destroyed. Because of their non-interference with operability, such miscellaneous metals are generally not mentioned in naming the composition or designating the formula of what essentially constitutes the zeolite. Similarly, as long as the amount of the miscellaneous metal ion is less than the amount of residual sodium ion, some or all of such miscellaneous metal ions may be introduced during an alkaline aging step instead of by ion exchange, while still retaining calcium sodium aluminodisilicate as the terminology for the ion exchanged zeolite.

One sample of sodium Zeolite A for Example XlV was prepared by aging the hot alkaline dispersion of meta kaolin. Another sample of sodium Zeolite A for Example XV was purchased from a manufacturer. The sodium Zeolite A samples of Examples XIV and XV are subjected to four steps of one hour of ion exchange with a 100 percent stoichiometric excess of hot solution of 1 molar CaCl The resulting calcium sodium alumino-disilicate is placed in quartz trays of about 30 x 23 X 8 cm and heated to about 1,000C. for about 60 minutes. The foamed slab is cooled and sawed into insulating panels about 2.5 cm thick. The insulating panels of Example XIV were prepared by the identical procedure of Example XV, the only difference being that Kumins type zeolite was the starting material in Example XIV and commercially available Zeolite A was the starting material in Example XV.

The panels are evaluated and shown to have properties including:

Panel Table Example XIV Example XV density 240g/l 240g]! shrinkage 0.6% after 24 hrs. 0.6% after 24 hrs.

at 2300F. at 2300"F. thennal conductivity 0.71 BTU/hL/ft'lin. 0.71 BTU/hL/lV/in. moisturc absorption 0.03 wt. after 24 0.03 wt. after 24 hrs. at relative humidity at about hrs. at 95% relative humidity at about 70F. 70F. compresive strength 1,75 lg/cm 1,75 lg/cm' :pecific pore volume 2.5 cc/g 2.5 cclg specific heat 0.22 callglC 0.22 callglC tant advantage for the foamed calcium sodium aluminodisilicate.

X-ray diffraction data concerning the foamed calcium sodium aluminodisilicate provided the basis for establishing an identification of the foamed calcium sodium aluminodisilicate, as set forth in appended Table A. The X-ray diffraction data confirmed the identity of the crystalline calcium sodium alumino-disilicate notwithstanding minor variations such as selection of commercially available Zeolite A or Kumins type of sodium alumino-disilicate as starting material, variations in the completion of the calcium exchange, presence or absence of minor amounts of modifier such as lithium, barium, or potassium, and size or shape of the structures such as panels made by the foaming.

The foamed calcium sodium aluminodisilicate was pulverized and the powder subjected to standard X-ray diffraction procedures to provide the following data:

TABLE A Such X-ray data suggest either a mixture possibly comprising nepheline, plagioclase and anorthite, or possibly a unique single crystalline species having no name other than foamed calcium sodium aluminodisilicate.

Foams in accordance with this invention have a volume shrinkage of less than about 0.7 percent when maintained at l250C for 24 hours; a moisture absorption of less than 0.1 percent when maintained at 95 percent relative humidity for 24 hours at ambient temperature; and a compressive strength of at least 1.5 kilograms per square centimeter.

Various modifications of the invention are possible without avoiding the scope of the claims.

We claim:

1. A low-density ceramic foam consisting essentially of calcium sodium aluminodisilicate. derived by thermal recrystallization, at conditions including a temperature in the range of 900l 150C for 10 to 120 minutes, of synthetic zeolite corresponding to )0.s-o.a'( 2 )o.1-o.s 2 s' 2') 2 in which y has a value such that the water content is 0.2-3 percent by weight of the zeolite, said ceramic foam characterized in having a. a plurality of uniformly distributed interconnected open pores contributing a porosity of at least volume percent, said open pores having diameters from about 5 to about 30 microns contributing about 75 percent of the porosity;

b. a crystalline composition substantially free of x-ray detectable zeolitic crystallinity;

c. a bulk density of less than 0.3 kilograms per liter;

d. a surface area of less than about 5 square meters e. a moisture absorption of less than 0.1 percent when maintained at percent relative humidity per 24 hours at ambient temperature;

f. a compressive strength of at least 1.5 kilograms per square centimeter;

g. a volume shrinkage of less than about 0.7 percent when maintained at l250C. for 24 hours; and

h. an initial fusion temperature of at least 1250C. 

